(1) Field of the Invention
The invention relates to a gravel packing apparatus and method for use in a subterranean well in a "thru-tubing" operation.
(2) Description of the Prior Art
Of considerable magnitude in the production of hydrocarbons, such as oil and gas, from a producing well is the problem of sand flow into the wellbore from unconsolidated formations. Production of sand with the flow of hydrocarbons will cause the wellbore to gradually fill-up with minute sand and silt particles until production perforations in the casing and, often times, the end of production tubing inserted therein, are covered, resulting in a significant reduction in fluid production. In many instances, sand production will cause the well to stop producing.
While such problem is frequently encountered in oil and gas wells, it will be appreciated that such problems are equally encounterable in water wells. Accordingly, it is contemplated that the invention has utility in abating this problem in water wells as well as oil and gas wells. Accordingly, by use of the term "subterranean well" herein, I mean to refer to and identify water, oil, gas, and other subterranean wells of similar nature. Accordingly, the use of the phrase "production zone" will refer to and mean a zone within any such well in which a fluid desired to be produced may be encountered, such as water, gas, oil, and/or mixtures thereof.
In addition to reduction of fluid production, flow of sand may also cause severe damage to equipment, such as pumps, chokes and the like. In flowing wells, fluid velocity may be sufficient to scavenge sand within the wellbore and produce it with the fluid hydrocarbon, resulting in holes being cut in the tubing and flow lines, as well as in valving components, such as the Christmas tree disposed at the top of the well through which production tubing and casing are communicated, connected or disposed.
When, referring to "Christmas tree" herein, I mean to refer to an assembly of valves and fittings which are attached to the upper most connection of the tubing head, used to control well production and which may be distinguished from a "wellhead" which includes all permanent equipment between the upper most portion of the surface casing and the tubing head adapter connection. A tubing head adapter adapts the upper most connection of a tubing head to the lower most valve of the Christmas tree.
One well known means of controlling flow of sand into the wellbore is the placement of gravel around the exterior of a slotted, perforated, or other similarly formed liner, isolation means, or screen. When used herein, all such references and constructions are the equivalent of the others and can be generally referred to as production or gravel pack screens. The selected construction of such components is not particularly significant to the present invention but the function of filtering out the sand produced with the oil or gas or water is common to all such constructions to thus prevent its entry into the wellbore and thence to the top of the well. It is important to size the gravel for proper containment of the sand. Additionally, the slotted liner, perforated pipe, or screen must be designed to prevent entry of the gravel or sand itself into the production tubing.
Most gravel pack assemblies incorporate two vertically spaced apart versions and sections of such "screens," with the lower section being commonly referred to as the "tell-tale" screen, and the second or higher screen assembly being referred to as the gravel pack screen. Two separate sections of screen bridge the perforated or production zone with the tell-tale screen being the first to receive the fluid returns interior of the apparatus during the gravel packing operation. As gravel is packed upwardly around the tell-tale screen and to the top of the gravel pack screen, an increase in fluid pumping pressure will be detected at the top of the well.
As described below, production of produced fluids in the zone will be conducted through the upper gravel pack packer, through the interior of the outer housing of the assembly remaining in the well after retrieval of the mandrel and cross-over tool components, thence through the opening in the lower end of the production conduit extending into the producing zone through the bore of a set production packer.
Although other fluids have been used, treated and filtered water with a desired concentration of chlorides plus a synthetic polymer or other shear thinning or viscosity controlling substance, is preferably used in most gravel packing processes during the packing and cleaning or flushing procedures. The water is treated to remove contaminants such as cement particles, scale, and other foreign material generally resulting from the circulation of fluid in the wellbore before recirculation into the well with additional gravel, or during any cleaning or flushing procedure.
Gravel packing may be effected as a portion of the initial completion operation or may be provided during a workover operation. Some present day workover operations contemplate the use of "thru-tubing" operations in which the production tubing remains in the well and the remedial or workover operation is effected through the production tubing by use of tubular conduits such as continuous coiled tubing, or the like. Such "thru tubing" tubular conduits may, of course, include a workover string of tubing made up of a series of tubing sections which are threaded or otherwise secured one to another and which are introduced into the well with the Christmas tree in place and through a selectively openable passageway through the Christmas tree and then concentrically disposed through the production tubing.
The present invention includes incorporation of expandable elastomeric packing elements which, because the operation will be performed "thru-tubing," preferably must be of a construction in which the sealing element of the inflatable packer is capable of expanding from the initial outer diameter during the running-in condition to the outer diameter when such packer is in the fully expanded condition of at least a ratio of two or more. Such packers are commercially available and are identified as the Model 373 Inflatable Packer made available by High Pressure Integrity, Inc., of New Orleans, La. The configuration of such packers is illustrated in Product Publication entitled "I-HIP Inflatable Tools" dated 1993, of High Pressure Integrity, Inc. New Orleans, La.
In U.S. Pat. No. 3,901,318, there is shown and disclosed a one trip gravel packing operation incorporating a fluid flow cross-over assembly which is moved to various positions by tubing manipulation. This patent contemplates traditional gravel packing operations and does not utilize an inflatable packer element, nor is the cross-over assembly utilized to provide a passageway to set the packer or to thereafter provide a passageway for introduction of the gravel and carrier fluid in the well nor to manipulate valvings by application of pressure subsequent to the setting of the packer. Moreover, tubing rotation is required during certain steps in the packer setting operation, as well as disengagement of the work string when it is desired to leave the gravel pack components in the well. Thus, where coiled tubing is to be the "thru tubing" component, the '318 tool cannot be used.
Likewise, U.S. Pat. No. 4,401,158, discloses the use of a similar device in concert with packing elements for multi-zone gravel packing and perforating of a well.
U.S. Pat. No. 4,627,488, discloses an isolation gravel packing system utilizing conventional mechanically set packers having slips and a cross-over tool disposed within the interior of the device for conventional isolation gravel packing with the device carried on a conventional work string into the well.
U.S. Pat. No. 4,856,590, utilizes coiled tubing in a thru-tubing operation, but utilizes a pre-packed screen apparatus.
U.S. Pat. No. 4,860,361, incorporates a coiled tubing string that does not require utilization of a cross-over assembly or multiple packers.
U.S. Pat. No. 5,219,025, incorporates a cross-over assembly to facilitate pumping of a gravel slurry in a wellbore and is of limited construction with respect to the configuration of the cross-over assembly.
U.S. Pat. No. 5,069,280, shows a variation of gravel packing incorporating a gravel packer which provides sequential locking and sealing of the packer in the well and includes a releasing mechanism for mechanically disconnecting it from the packer.
U.S. Pat. No. 5,174,379, discloses a single trip gravel packing and perforating operation typical of the prior art in such combination.
U.S. Pat. No. 5,332,038, discloses a gravel packing system incorporating a combination packer and setting tool for the packer which is mechanically set. U.S. Pat. No. 5,343,953, discloses a thru-tubing recirculating device incorporating a cross-over assembly and a gravel packing screen.
U.S. Pat. No. 5,377,749, teaches the introduction of coiled tubing through a wellhead and the utilization of a mechanically set packer with a flow control cross-over assembly for providing a fluid flow path for gravel packing only. The packer disclosed in this patent is of extremely restricted expansion and requires mechanical manipulation of the tubing string for the setting.
U.S. Pat. No. 5,413,176, is directed to a device for repairing a gravel packing screen already in place, and incorporates a mechanically set packing device.
U.S. Pat. No. 5,609,204, discloses a gravel packing device incorporating a cross-over assembly and a mechanically set packer with a washpipe stabbed into a seal bore bridging the production screen.
U.S. Pat. No. 5,620,050, discloses a method for setting a hydraulic packer used in a gravel packing operation on remedial coiled tubing disposed through a wellhead. The packer is set hydraulically. This patent discloses hydraulic actuation of a conventional non-elastomeric expansible packer which incorporates slips for purposes of anchoring the packer against the inner wall of the well. Moreover, this patent does not use a flow control cross-over assembly with concentrically disposed flow passageways therethrough that can be used to both set the packer and open certain valves to circulate the gravel and carrier fluid.
Promotional literature entitled "Eclipse Series Packers/Plugs for Coiled Tubing" discloses the use of a conventional non-inflatable packer with slips and a cross-over assembly in which a passageway in the cross-over assembly is utilized to transmit pressure to mechanically move the slips and the conventional packer into set position. Only one packer is utilized and the cross-over assembly cannot be used to provide setting of plural packers because one of the concentric passageways through the cross-over assembly permits fluid flow therethrough in only one direction, i.e., to the top of the well, for returns.
Electric line gravel packing is an alternative to the thru-tubing concept, and is typified in U.S. Pat. No. 5,033,549. Likewise, U.S. Pat. No. 5,115,860 discloses a similar method of implementing a thru-tubing gravel packing operation.
Finally, Society of Petroleum Engineers Paper No. 23130 entitled "Thru-Tubing Sand Control Techniques Reduce Completion Costs," presented at Offshore Europe Conference held in Aberdeen, Scotland, Sep. 3-6, 1991, generally discloses commercially available gravel packing components and tools as well as various types of perforated tubing, screens, and slotted liners, which may be incorporated into the present invention.